No RPM

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No RPM

Postby Chris944 » Tue Aug 08, 2017 8:05 pm

Hello everybody, I know this is not a new topic, I have searched and done what some have suggested for other people's projects with no luck. I have a Megastim v 2.21 and a megasquirt 2 V 3.0. All other parts of the stim work amazingly! So, I am thinking that it must be something in the circuit on the Megasquirt. Where should I begin looking? Thank you so much for your help and patience. - Chris
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Re: No RPM

Postby billr » Tue Aug 08, 2017 10:02 pm

Post the MSQ, and post a picture of the stim that shows the jumpers/switches on the stim, if it has any. I'm wondering (from the version) if this is actually a "Jimstim"?
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Re: No RPM

Postby phongshader » Fri Sep 01, 2017 6:40 pm

Hi, I want to get in on this as well. I'm unable to get a tach/rpm out or into my MS as well. This is a fuel only setup driven off the - coil terminal. I've followed these steps:
Install and solder D1 {1N4001DICT-ND}. This is the famous Wing Diode - you will want this if you are triggering off the negative side of the coil - such as with points (reduces tach signal false-triggering).
In the place of D2, install a 22V or 24V Zener diode {1N4748A-ND}, in the reverse of the indicted orientation (i.e., put the band at the other end rather than that indicated on the silk screen).

If you are going to use the negative side of the coil to trigger MegaSquirt® (I.e., you are not using ignition timing control), then install and solder C30 {399-4353-ND, 0.22µF, 224 marking}.
If you are going to use the negative side of the coil to trigger MegaSquirt® (I.e., you are not using ignition timing control), then install and solder C12, the Ed capacitor (399-4202-ND, 0.001 µF, 102 marking}. This is located above "Bowling" in the copyright notice. The value of this capacitor may need to be increased if there are noise problems with the tach signal - values up to 0.1µF will work. The 0.001µF value is a good starting point.

I've jumped D2 to work with a JimStim 1.5, no rpm, tried jumping D1, still no rpm. tried it on the car no rpm. The JimStim is v1.5, firmware v2.0.3, the wheel selector dip switch is all off for dstributor/edis, primary tach signal is jumpered to Hall, and jumpered to a 12v pullup for primary tach signal. TunerStudio is set to fuel only in Ignition Options/Wheel Decoder.
Let's test the opto input circuit. With the Megasquirt powered up, apply 12 volts to pin 24 or TachSelect, and check the voltage on the TSEL jumper with a voltmeter. You should read zero volts. Next, ground pin 24 so it has no volts on the input circuit, and check TSEL's voltage again. You should see 5 volts there.

I've seen this posted as a way to test if the opto input circuit but I'm unclear as to where I place the -probes of the voltmeter, that is when testing +12v to pin 24/TachSelect where is the -probe measuring from, ground on the stim or -12v on the stim? Same for when applying -12v to pin 24/TachSelect. Right now I get no volts at at TSEL regardless of + or -12v at pin24 when grounding at the ground header on the JimStim.

This is all going on a 1970 Buick Skylark 350 V8
ms2, v3 board, ms2 extra 3.4.0
Attachments
2017-09-01_17.20.53_Skylark.msq
current msg with no rpm
(119.15 KiB) Downloaded 12 times
MSII, V2.2, LC-1
Olds 215 v8 in a '59 Alfa Romeo Spider 2000
-------------------------------------------------
MS3/3X, LC-1
Duratec 2.3, GSXR itb, Locost
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Re: No RPM

Postby Matt Cramer » Tue Sep 05, 2017 9:01 am

The JimStim's ground pin will work for this test.
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Re: No RPM

Postby phongshader » Tue Sep 26, 2017 7:00 am

It turns out that U3/optoisolator was bad, replaced it and I'm up and running...well at least started.
MSII, V2.2, LC-1
Olds 215 v8 in a '59 Alfa Romeo Spider 2000
-------------------------------------------------
MS3/3X, LC-1
Duratec 2.3, GSXR itb, Locost
User avatar
phongshader
Experienced MS/Extra'er
 
Posts: 155
Joined: Sat Jan 15, 2005 10:37 pm


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